This invention relates to environmental testing of electronic circuits and, more particularly, to methods and apparatus for evaluating electronic circuit operation in response to different power supply slew times.
Environmental testing is widely used to confirm that electronic circuits will operate as intended under a variety of environmental conditions. Such conditions include, for example, temperature variations, humidity variations, voltage variations and vibration. In such testing, the electronic circuit is subjected to a range of environmental conditions, and operation of the circuit is evaluated. The range of environmental conditions corresponds to and frequently exceeds the range of environmental conditions expected during normal operation. Thus, if the circuit operates according to specification during environmental testing, it can be expected to operate according to specification during normal operation.
Environmental testing may utilize a variety of protocols. An engineering qualification test may be utilized to evaluate a new circuit design. Production environmental testing may be used identify early failures and defects and to thereby increase the probability that each circuit will operate satisfactorily when it is installed in a system and operated under normal conditions. Production testing may involve sampling or 100% testing of production circuits. Environmental testing may be performed at various levels, such as chip level, printed circuit board level and subassembly level.
Notwithstanding the exhaustive nature of prior art environmental testing, it has been found that certain defects are not detected by current environmental test procedures. As used herein, the term xe2x80x9cdefectxe2x80x9d refers to a failure of the electronic circuit to operate according to specification. In particular, an electronic circuit may pass all prior art environmental tests and yet fail to operate properly when it is installed in a system and operated under normal conditions. It is therefore desirable to provide enhanced environmental test methods and apparatus which will identify such defects and thereby increase the integrity of environmental testing.
According to a first aspect of the invention, a method is provided for testing a unit that requires a power supply for operation. The method comprises the step of applying to a unit under test a power supply having a test slew time that is selected to evaluate operation of the unit under test in a system, observing a response of the unit under test to the power supply having the test slew time and determining the condition of the unit under test based on the response of the unit under test to the power supply having the test slew time.
The step of applying the power supply may include applying the power supply with a maximum test slew time and applying the power supply with a minimum test slew time. In one embodiment, the maximum test slew time may be equal to a maximum operating slew time, and the minimum test slew time may be equal to a minimum operating slew time. In another embodiment, the maximum test slew time may exceed the maximum operating slew time, and the minimum test slew time may be less than the minimum operating slew time. The slew time may be controlled by controlling the slew time of a programmable power supply.
According to another aspect of the invention, apparatus is provided for testing a unit that requires a power supply for operation. The apparatus comprises a programmable power supply for applying to a unit under test a supply voltage with a test slew time that is selected to evaluate operation of the unit under test in a system, and a test device for observing a response of the unit under test to the supply voltage with the test slew time and determining the condition of the unit under test based on the response.
According to a further aspect of the invention, a method is provided for testing a unit that requires a power supply for operation. The method comprises the steps of applying to a unit under test a power supply having a maximum test slew time, applying to the unit under test the power supply having a minimum test slew time, observing the responses of the unit under test to the power supply having the maximum and minimum test slew times, and determining the condition of the unit under test based on the responses of the unit under test.
According to yet another aspect of the invention, a method is provided for testing a unit that requires a power supply for operation. The method comprises the steps of controlling a programmable power supply to generate voltages having one or more test slew times selected to evaluate a unit under test, applying the power supply voltages with the selected test slew times to a unit under test, observing the responses of the unit under test to the power supply voltages with the selected test slew times, and determining the condition of the unit under test based on the responses of the unit under test to the power supply voltages with the selected test slew times.